feat(Rest): show the data that is sent to Discord when an errors occurs (#5701)

src/rest/HTTPError.js

@@ -5,7 +5,7 @@
  * @extends Error
  */
 class HTTPError extends Error {
-  constructor(message, name, code, method, path) {
+  constructor(message, name, code, request) {
     super(message);
 
     /**
@@ -24,13 +24,36 @@ class HTTPError extends Error {
      * The HTTP method used for the request
      * @type {string}
      */
-    this.method = method;
+    this.method = request.method;
 
     /**
      * The path of the request relative to the HTTP endpoint
      * @type {string}
      */
-    this.path = path;
+    this.path = request.path;
+
+    /**
+     * The HTTP data that was sent to Discord
+     * @typedef {Object} HTTPErrorData
+     * @property {*} json The JSON data that was sent
+     * @property {HTTPAttachmentData[]} files The files that were sent with this request, if any
+     */
+
+    /**
+     * The attachment data that is sent to Discord
+     * @typedef {Object} HTTPAttachmentData
+     * @property {string} name The file name
+     * @property {Buffer} file The file buffer
+     */
+
+    /**
+     * The data associated with the request that caused this error
+     * @type {HTTPErrorData}
+     */
+    this.requestData = {
+      json: request.options.data,
+      files: request.options.files ?? [],
+    };
   }
 }